Deep long-slit spectroscopic data are presented for a sample of 14 3CR radio galaxies at redshift z ~ 1, previously studied in detail using the Hubble Space Telescope, the Very Large Array, and UKIRT. Analysis of the [OII] 3727 emission line structures at 5 Ang spectral resolution is carried out to derive the kinematic properties of the emission line gas. In line with previous, lower resolution, studies, a wide variety of kinematics are seen, from gas consistent with a mean rotational motion through to complex structures with velocity dispersions exceeding 1000 kms. The data confirm the presence of a high velocity gas component in 3C265 and detached emission line systems in 3C356 and 3C441, and show for the first time that the emission line gas in the central regions of 3C324 is composed of two kinematically distinct components. Emission line fluxes and the colour of the continuum emission are determined down to unprecedently low observed wavelengths, lambda < 3500 Ang, sufficiently short that any contribution of an evolved stellar population is negligible. An accompanying paper investigates the variation in the emission line ratios and velocity structures within the sample, and draws conclusions as to the origin of the ionisation and kinematics of these galaxies.
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